This research project consists of investigations of changes in laryngeal muscle activity with age and treatment. The long-range aims are to document physiologic characteristics of the normal aging larynx and evaluate the response to behavioral treatment. These normative data will be useful for differential diagnosis of laryngeal disorders and to understand the age-related changes in mechanisms of fundamental frequency and intensity control. Specific aims are to: 1) determine age-related changes in fundamental frequency and intensity ranges in sustained phonation and speech; 2) determine patterns of cricothyroid (CT) and thyroarytenoid (TA) muscle activation and concomitant lung pressure estimates during changes in the fundamental frequency and intensity of phonation in young and old subjects; 3) relate the known reductions in phonatory stability of the elderly voice (jitter, shimmer, tremor, quaver) to reductions in the stability of the frequency of firing and recruitment of motor units of laryngeal muscles and /or variations in lung pressure estimates; 4) determine if and how a behavioral voice therapy known to be efficacious for improving phonation and intelligibility in patients with Parkinson's disease (Lee Silverman Voice Treatment; LSVF) can counteract the acoustic and neuromuscular changes associated with the voice characteristics of normal elderly people. Findings from this work will contribute to knowledge about aging and improving communication skills in older populations.